Kinetochore life histories reveal an Aurora-B-dependent error correction mechanism in anaphase

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An Efficient Regression Type Estimator in Survey Sampling

For the estimation of population mean in simple random sampling, an efficient regression-type estimator is proposed which is more efficient than the conventional regression estimator and hence than mean per unit estimator, ratio and product estimators and many other estimators proposed by various authors. Some numerical examples are included for illustration.     

On blocking rules for the bootstrap with dependent data

We address the issue of optimal block choice in applicationsof the block bootstrap to dependent data. It is shown that optimalblock size depends significantly on context, being equal ton^1/3, n^1/4 and n^1/5 in the cases of variance or bias estimation,estimation of a onesided distribution function, and estimationof a two-sided distribution function, respectively. A clearintuitive explanation of this phenomenon is given, togetherwith outlines of theoretical arguments in specific cases. Itis shown that these orders of magnitude of block sizes can beused to produce a simple, practical rule for selecting blocksize empirically. That technique is explored numerically.     

Can We Accurately Characterize Wildlife Resource Use When Telemetry Data Are Imprecise?

ABSTRACT Telemetry data have been widely used to quantify wildlife habitat relationships despite the fact that these data are inherently imprecise. All telemetry data have positional error, and failure to account for that error can lead to incorrect predictions of wildlife resource use. Several techniques have been used to account for positional error in wildlife studies. These techniques have been described in the literature, but their ability to accurately characterize wildlife resource use has never been tested. We evaluated the performance of techniques commonly used for incorporating telemetry error into studies of wildlife resource use. Our evaluation was based on imprecise telemetry data (mean telemetry error = 174 m, SD = 130 m) typical of field-based studies. We tested 5 techniques in 10 virtual environments and in one real-world environment for categorical (i.e., habitat types) and continuous (i.e., distances or elevations) rasters. Technique accuracy varied by patch size for the categorical rasters, with higher accuracy as patch size increased. At the smallest patch size (1 ha), the technique that ignores error performed best on categorical data (0.31 and 0.30 accuracy for virtual and real data, respectively); however, as patch size increased the bivariate-weighted technique performed better (0.56 accuracy at patch sizes >31 ha) and achieved complete accuracy (i.e., 1.00 accuracy) at smaller patch sizes (472 ha and 1,522 ha for virtual and real data, respectively) than any other technique. We quantified the accuracy of the continuous covariates using the mean absolute difference (MAD) in covariate value between true and estimated locations. We found that average MAD varied between 104 m (ignore telemetry error) and 140 m (rescale the covariate data) for our continuous covariate surfaces across virtual and real data sets. Techniques that rescale continuous covariate data or use a zonal mean on values within a telemetry error polygon were significantly less accurate than other techniques. Although the technique that ignored telemetry error performed best on categorical rasters with smaller average patch sizes (i.e., ≤31 ha) and on continuous rasters in our study, accuracy was so low that the utility of using point-based approaches for quantifying resource use is questionable when telemetry data are imprecise, particularly for small-patch habitat relationships.     

Gene assignment by means of somatic cell hybrids: a new method for the analysis of data

Summary A statistical approach to the interpretation of data from gene assignment with somatic cell hybrids is presented. The observed data are analysed under a variety of hypotheses. The fit to the hypotheses is compared by means of the likelihood obtained under a given hypothesis. Two of these hypotheses are related to fundamental questions: is a gene responsible for the enzyme observation and if so, is that gene located on a specific chromosome or could it change its position and be sometimes on chromosome j and, in another hybrid line, on chromosome k? The other hypotheses concern the assignment of the gene to just one of the chromosomes.To improve the traditional data analysis approach we considered additional information: the uncertainties and possible errors of laboratory methods in all our calculations and the length of the donor chromosomes in connection with one specific hypothesis.This method allows us to account for the reliability of the investigation methods and the nature of the hybrid lines involved. Data can be evaluated at different error probabilities within a realistic range in order to compare and discuss results.     

Estimation of uncertainties in X-ray refinement results by use of perturbed structures

The uncertainties in the refined parameters for a 1.5-A X-ray structure of carbon-monoxy (FeII) myoglobin are estimated by combining energy minimization with least-squares refinement against the X-ray data. The energy minimizations, done without reference to the X-ray data, provide perturbed structures which are used to restart conventional X-ray refinement. The resulting refined structures have the same, or better, R-factor and stereochemical parameters as the original X-ray structure, but deviate from it by 0.13 A rms for the backbone atoms and 0.31 A rms for the sidechain atoms. Atoms interacting with a disordered sidechain, Arg 45 CD3, are observed to have larger positional uncertainties. The uncertainty in the B-factors, within the isotropic harmonic motion approximation, is estimated to be 15%. The resulting X-ray structures are more consistent with the energy parameters used in simulations.     

Test of circular dichroism (CD) methods for crambin and CD-assisted secondary structure prediction of its homologous toxins

Methods that analyze protein circular dichroism (CD) spectra for fractions of secondary structure are evaluated for the plant protein crambin, which has a known high-resolution crystal structure. In addition, a two-step secondary structure prediction scheme is presented and used for the toxins homologous to crambin, shown by others to have secondary structures similar to crambin. The test of CD spectral analysis methods with the protein crambin employed two computer programs and several CD basis sets. Crambin's crystal structure, known to 0.945A resolution (Hendrickson, W.A., Teeter, M.M. Nature 290:107-113, 1981), allows accurate evaluation of results. Analysis with the protein spectra basis sets (Provencher, S.W., Gl?ckner, J. Biochemistry 20:33-37, 1981) as modified (Manavalan, P., Johnson, W.C., Jr. Anal. Biochem. 167:76-85, 1987) agreed most closely with crambin's crystal structure. This method was then applied to the CD spectra of the membrane-active toxins homologous to crambin (alpha 1- and beta-purothionin, phoratoxin A and B, and viscotoxin A3 and B). The new program SEQ (pronounced "seek") was developed to assign the secondary structure along the protein chain in a hierarchical fashion and applied to the plant toxins. The method constrained the secondary structure fractions to those from CD analysis and combined standard statistical methods with amphipathic helix location. Both CD-arrived secondary structure percentages and sequence assignment indicate that the viscotoxins are structurally most similar to crambin. Purothionin's secondary structure was predicted to be fundamentally similar to crambin's with a difference at the start of the first helix. This assignment agreed with Raman and NMR analyses of purothionin and lends validity to the method presented here. Differences from the NMR in the CD secondary structure fraction analysis for phoratoxin suggest interference in the CD from tryptophan residues.     

A triple-resonance pulse scheme for selectively correlating amide1HN and15N nuclei with the1Hα proton of the preceding residue

Summary A 3D¹H–¹⁵N–¹³C triple resonance experiment is presented that contains exclusively cross peaks between the¹H^N and¹⁵N nuclei of one residue with the H of the preceding residue. The pulse sequence, designed to minimize the time coherence, is transverse on nuclei with short T₂ values. The experiment consists of coherence transfers via one-bond couplings from the H^N via N, CO, C to the H and back to the H^N for detection; it is called HN(COCA)HA. The experiment was tested on uniformly¹⁵N- and¹³C-enriched T4 lysozyme.